Conventionally, there have been technologies for mounting semiconductor light-emitting devices made of light-emitting diode onto a substrate by using wire bonding or flip-chip mounting. Because those technologies require high precision placement, such a light-emitting device is expected that it can be mounted in batch process using surface-mount technology.
Recently, a light-emitting device using nitride semiconductors is largely applied as a semiconductor light-emitting device. Such a light-emitting device is manufactured by depositing semiconductors on a sapphire substrate, so lights from such a device are extracted through the transparent sapphire substrate. However, there exist differences of index of refraction between semiconductor thin film and sapphire substrate, and also between sapphire substrate and the atmosphere, and thus a part of lights is confined in a chip of the device and radiated as heat. In the case that the lights are extracted from the semiconductor surface opposite to the sapphire substrate and lights do not go through the sapphire substrate, therefore the device can be mounted at the sapphire substrate side, however heat release efficiency is not good because of the interposition of sapphire substrate. Thus such a technology is proposed that the sapphire substrate is removed and a heat sink is attached on the place where the substrate is removed (e.g., Japanese Laid-Open Patent Publication No. 2000-196197).
Subsequently, above-mentioned technology, removing the sapphire substrate, is described. This technology is used in the production of laser diode array which is a collective of multiple laser diodes. FIG. 19A-19F show a series of laser diode array manufacturing process. As shown in FIG. 19A, a laser diode array is made on the sapphire substrate with thin film layers of semiconductor 102 and electrodes 121. Next, as shown in FIG. 19B, the surface provided with electrodes 121 and is opposite to the sapphire substrate is glued with the wax 103 to the support substrate 104 to support the array including the sapphire substrate.
In this situation, by applying laser beams 105 to the semiconductor 102 through the sapphire substrate, thin GaN layer pre-formed on the surface of the semiconductor 102 is decomposed to metal Ga and N2, and as shown in FIG. 19C, the sapphire substrate is separated and is removed.
In the next step, as shown in FIG. 19D, a metal layer 106 is formed on the surface of the semiconductor 102, where the sapphire substrate was removed, and thermal conductive substrate 108 is prepared which has a metal layer 107 (if metal substrate is used, metal layer 107 is not necessary). Next, as shown in FIG. 19E, semiconductor 102 and thermal conductive substrate (heat sink) 108 are bonded at each metal layer by solder layer 109. As shown in FIG. 19F, wax 103 is melted to complete laser diode array which is composed of semiconductor 102 and electrodes 121 supported on the thermal conductive substrate 108.
As described above, by removing a sapphire substrate, and attaching a thermal conductive substrate on a place where the sapphire substrate existed, flip side contacts on common surface can be made for all laser diodes in the array. Besides, heat sink is effectively used. The technology to remove a sapphire substrate can be applied not only to a laser diode but also to a semiconductor light-emitting device such as a light-emitting diode (LED).
However, as to above-mentioned method to remove a sapphire substrate, to form electrodes, or to bond a heat sink as shown in FIG. 19A-19F or patent document, many process steps are necessary, and the cost for preparing the support substrate is high. Moreover, since light beams are extracted from the surface where electrodes are provided, there is a problem that the light extraction efficiency of the light-emitting device becomes low.